Conventionally, as a tire used for a snow-covered road surface, there has been known a tire including a block partitioned by a groove portion that includes a circumferential groove positioned at the outer side in a tread width direction from a tire equator line and extending in a tire circumferential direction and a lug groove extending in the tread width direction (see Patent Literature 1, for example). For example, in the tire of the Patent Literature 1, two block arrays in which a plurality of blocks are arranged in the tire circumferential direction are formed.
As described above, the block partitioned by the groove portion includes an edge portion biting into a snow surface to rub against the snow, and thus, the aforementioned tire has a snow traction performance. Furthermore, snow having entered the groove portion is trodden down by loads of the tire and a vehicle to form snow columns. The aforementioned tire is imparted with a snow traction performance by a snow shearing force effect obtained by kicking out the snow columns.